1. Field of the Invention
Embodiments of the present invention relate generally to x-ray devices. More particularly, embodiments of the present invention relate to devices, systems and methods for cooling evacuated enclosure windows employed in x-ray devices.
2. Related Technology
The x-ray tube has become essential in medical diagnostic and inspection imaging, medical therapy, and various medical testing and material analysis industries. Such equipment is commonly employed in areas such as medical and industrial diagnostic examination, therapeutic radiology, semiconductor fabrication, and materials analysis.
An x-ray tube typically includes a vacuum enclosure that contains a cathode assembly and an anode assembly. The vacuum enclosure may be composed of metals, glass, ceramic, or a combination thereof, and is typically disposed within an outer housing. A cooling medium, such as a dielectric oil or similar coolant, can be disposed in the volume existing between the outer housing and the vacuum enclosure in order to dissipate heat from the surface of the vacuum enclosure. Depending on the configuration, heat can be removed from the coolant by circulating the coolant to an external heat exchanger via a pump and fluid conduits. The cathode assembly generally consists of a metallic cathode head assembly and a source of electrons highly energized for generating x-rays. The anode assembly, which is generally manufactured from a refractory metal such as tungsten, includes a focal track that is oriented to receive electrons emitted by the cathode assembly.
The evacuated enclosure includes an evacuated enclosure window aligned with the focal track such that x-rays emitted from the focal track can pass out of the evacuated enclosure. The evacuated enclosure window is typically disposed in a port formed in a wall of the evacuated enclosure and is attached to the evacuated enclosure by welding, brazing, or other methods.
During operation of the x-ray tube, the anode is rotated and the cathode is charged with a heating current that causes electrons to escape the electron source or emitter. An electric potential is applied between the cathode and the anode in order to accelerate the emitted electrons toward the annular focal track of the anode. X-rays are generated by a portion of the highly accelerated electrons striking the annular focal track.
In order to produce high-quality x-ray images, it is generally desirable to maximize x-ray flux, i.e., the number of x-ray photons emitted per unit time. X-ray flux can be increased by increasing the number of electrons emitted by the electron emitter that impinge on the focal track.
However, many of the electrons that strike the focal track are backscattered from the focal track towards the evacuated enclosure window. The number of backscatter electrons is generally proportional to the number of electrons that impinge on the focal track. When the backscattered electrons strike the evacuated enclosure window, a significant amount of their kinetic energy is transferred to the evacuated enclosure window as thermal energy. Without an effective cooling mechanism, the evacuated enclosure window can overheat and fail, thereby compromising the evacuated enclosure and the ability of the x-ray tube to operate. Accordingly, because the number of backscatter electrons is proportional to the number of electrons that impinge on the focal track, the cooling inefficiency of the x-ray tube effectively imposes a limit on the maximum number of electrons that can be emitted by the electron emitter toward the focal track, and, as a result, on the quality of the x-ray images produced by the x-ray tube.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced